Short Version: The Consigliere of a crime family is also known as the adviser to the boss.
Description of a Consigliere
Consiglieres act as a mediator of disputes as well as being representatives in meetings with other families. They often keep the family looking as legitimate as possible and are sometimes themselves legitimate apart from some minor gambling or loan sharking.
Consiglieres are also often the liaison between the boss of the crime family and important figures, such as politicians or judges. They are one of the few members of a family that can argue with the boss on certain decisions or plans, because of the nature of the job. This means a Consigliere cannot just be a yes man.
A Consigliere overall needs to be someone that the boss has ultmiamte faith and trust in, because this position opens up all of the crime family secrets, from plans to the most important contacts. Usually Consigliere’s are also off limits to being a target by other families.